Those skilled in the art understand that a wireless local area network (WLAN) may commonly use orthogonal frequency division multiplexing (OFDM) for communications between an access point (AP) and one or more client stations (STAs). OFDM is a transmission format where all transmission resources are allocated to a single STA at a time. The AP or STA wins access to the medium using a contention access technique (such as carrier sense multiple access with collision avoidance (CSMA/CA), and then transmits its data for up to a pre-defined time period. The medium is then relinquished for the AP or other stations to compete for access and use.
There is considerable interest in the art for the use of orthogonal frequency division multiple access (OFDMA) techniques in the WLAN. One reason for this interest is that OFDMA presents a transmission and access mechanism that would accommodate simultaneous transmissions with respect to multiple STAs. OFDMA is not a new technology as it has been used in many other communications schemes. Extension of OFDMA to WLAN, however, is a challenge because WLAN is a well-established and regulated technology (see, for example, the standardized implementations in IEEE 802.11). Frame structure and scheduling of resources must be fit within existing WLAN signaling and restrictions.
There is accordingly a need in the art for a messaging structure to control sub-channel allocation on both the down-link (DL—i.e., from the AP to one or more STAs) and the up-link (UL—i.e, from one or more STAs to the AP).